Drop on demand ink jet technology is widely used in the printing industry. Printers using drop on demand ink jet technology can use either thermal ink jet technology or piezoelectric technology. Even though they are more expensive to manufacture than thermal ink jets, piezoelectric ink jets are generally favored as they can use a wider variety of inks and eliminate problems with kogation.
Piezoelectric ink jet print heads typically include a flexible diaphragm manufactured from, for example, stainless steel. Piezoelectric ink jet print heads can also include an array of individual piezoelectric transducers (i.e., PZT or actuator) attached to the diaphragm. Other structures can include one or more laser-patterned dielectric standoff layers and a flexible printed circuit (flex circuit) or printed circuit board (PCB) electrically coupled with each transducer. A print head can further include a body plate, an outlet plate, and an aperture plate, each of which can be manufactured from stainless steel. Additionally, a print head can include various adhesive layers, for example laser-patterned adhesive layers, to hold each structure together and to provide an ink pathway from an ink reservoir, through the print head, and out a plurality of nozzles in the aperture plate.
During use of a piezoelectric print head, a voltage is applied to a piezoelectric transducer, typically through electrical connection with a flex circuit electrode electrically coupled to a voltage source, which causes the piezoelectric transducer to bend or deflect, resulting in a flexing of the diaphragm. Diaphragm flexing by the piezoelectric transducer expels a quantity of ink from a chamber through a particular nozzle (i.e., one or more openings) in the aperture plate. The flexing further draws ink into the chamber from a main ink reservoir through an opening to replace the expelled ink.
As resolution and density of the print heads increase, the area available to provide electrical interconnects decreases. Routing of other functions within the head, such as ink feed structures and electrical interconnects, compete for this reduced space and place restrictions on the types of materials used. For example, current technology for use with a 600 dots-per-inch (DPI) print head can include parallel electrical traces on the flex circuit with each trace electrically connected to a pad (i.e., electrode) of the pad array (i.e., electrode array) of the flex circuit. The parallel traces can have a 38 micrometer (μm) pitch and a 16 μm trace width, thereby leaving a 22 μm space between each trace. As print head densities increase, current flex circuit design practices will require formation of traces and pads having tighter tolerances and smaller feature sizes.
Methods for manufacturing a print head which can have improved reliability, yields, and scalability, and the resulting print head, would be desirable.